UIInterfaceOrientation orientation = [[UIDevice currentDevice] orientation];
The UIInterfaceOrientation is an enum:
typedef enum {
UIInterfaceOrientationPortrait = UIDeviceOrientationPortrait,
UIInterfaceOrientationPortraitUpsideDown = UIDeviceOrientationPortraitUpsideDown,
UIInterfaceOrientationLandscapeLeft = UIDeviceOrientationLandscapeLeft,
UIInterfaceOrientationLandscapeRight = UIDeviceOrientationLandscapeRight
} UIInterfaceOrientation;